Multiple sclerosis (MS) is a demyelinizing disease of the central nervous system (CNS) of which the complete cause still remains unknown.
Numerous studies have supported the hypothesis for a viral etiology of the disease, but none of the known viruses tested has proved to be the causative agent tested for: a review of the viruses tested for in MS for many years has been carried out by E. Norrby and R. T. Johnson.
Recently, a retrovirus, different from the known human retroviruses, was isolated from patients suffering from MS. The authors were able to show that this retrovirus could be transmitted in vitro, that patients suffering from MS produced antibodies capable of recognizing proteins associated with the infection of the leptomeningeal cells by this retrovirus, and that the expression of the latter could be greatly stimulated by the immediate-early genes of some herpesviruses.
All these results argue in favor of the role in MS of at least one unknown retrovirus or of a virus having a reverse transcriptase (RT) activity which is detectable by the method published by H. Perron and termed “LM7-type RT” activity.
The studies by the applicant have made it possible to obtain two continuous cell lines infected with natural isolates obtained from two different patients suffering from MS, by a culture method as described in the document WO-A-93 20188, whose content is incorporated by reference into the present description. These two lines derived from cells of human choroid plexus, called LM7PC and PLI-2, were deposited at the E.C.A.C.C. on 22 Jul. 1992 and 8 Jan. 1993, respectively, under numbers 92 072201 and 93 010817, in accordance with the provisions of the Treaty of Budapest. Moreover, the viral isolates possessing an LM7-type RT activity have also been deposited at the E.C.A.C.C. under the overall name of “strains”. The “strain” or isolate harbored by the PLI-2 line, called POL-2, was deposited at the E.C.A.C.C. on 22 Jul. 1992 under No. V92072202. The “strain” or isolate harbored by the LM7PC line, called MS7PG, was deposited at the E.C.A.C.C. on 8 Jan. 1993 under No. V93010816.
Using the above-mentioned cultures and isolates, characterized by biological and morphological criteria, efforts were then made to characterize the genetic material associated with the viral particles produced in these cultures.
The proportions of genome already characterized were used to develop molecular detection tests for the viral genome and immunoserological tests, using the amino acid sequences encoded by the nucleotide sequences of the viral genome, in order to detect the immune response directed against epitopes associated with the viral infection and/or expression.
These tools have already made it possible to confirm an association between MS and the expression of the sequences identified in the patents cited further on. However, the viral system discovered by the applicant is related to a complex retroviral system. Indeed, the sequences which are found to be encapsidated in the extracellular viral particles produced by the different cultures of cells of patients suffering from MS show clearly that there is co-encapsidation of retroviral genomes which are related but different from the “wild-type” retroviral genome which produces the infectious viral particles. This phenomenon was observed between replicative retroviruses and endogenous retroviruses belonging to the same family, or even heterologous retroviruses. The concept of endogenous retrovirus is very important in the context of our discovery because, in the case of MSRV-1, it has been observed that endogenous retroviral sequences comprising sequences homologous to the MSRV-1 genome exist in normal human DNA. The existence of endogenous retroviral elements (ERV) related to MSRV-1 through all or part of their genome explains the fact that the expression of the MSRV-1 retrovirus in human cells can interact with related endogenous sequences. These interactions are found in the case of pathogenic and/or infectious endogenous retroviruses (for example some ecotropic strains of the Murine Leukemia virus), in the case of exogenous retroviruses whose nucleotide sequence may be found partially or completely in the form of ERVs, in the genome of the host animal (e.g. mouse mammary tumor exogenous virus transmitted via milk). These interactions consist mainly of (i) a transactivation or co-activation of ERVs by the replicative retrovirus, (ii) an “illegitimate” encapsidation of related RNAs of ERVs, or of ERVs—or even of cellular RNAs—simply possessing compatible encapsidation sequences, into the retroviral particles produced by the expression of the replicative strain, which are sometimes transmissible and sometimes with an inherent pathogenicity, and (iii) relatively high recombinations between the co-encapsidated genomes, in particular in the reverse transcription phases, which lead to the formation of hybrid genomes, which are sometimes transmissible and sometimes with an inherent pathogenicity.
Thus, (i) various MSRV-1-related sequences have been found in purified viral particles; (ii) molecular analysis of the various regions of the MSRV-1 retroviral genome should be carried out by systematically analyzing the co-encapsidated, interfering and/or recombinant sequences which are generated by the infection and/or expression of MSRV-1; furthermore, some clones may have portions of defective sequences produced by the retroviral replication and the template and/or transcription errors caused by reverse transcriptase; (iii) the families of sequences related to the same retroviral genomic region are the supports for an overall diagnostic detection which may be optimized by the identification of invariable regions among the clones expressed and by the identification of reading frames responsible for the production of antigenic and/or pathogenic polypeptides which may only be produced by a portion, or even only one, of the clones expressed and under these conditions, the systematic analysis of the clones expressed in one region of a given gene makes it possible to evaluate the frequency of variation and/or recombination of the MSRV-1 genome in this region and to define the optimum sequences for the applications, in particular the diagnostic applications; (iv) the pathology caused by a retrovirus such as MRSV-1 may be a direct effect of its expression and of the proteins or peptides produced as a result, but also an effect of the activation, encapsidation, recombination of related or heterologous genomes and proteins or peptides produced as a result; thus, these genomes associated with the expression and/or infection by MSRV-1 are an integral part of the potential pathogenicity of this virus and therefore constitute diagnostic detection supports and particular therapeutic targets. Likewise, any agent which is associated with, or which is a cofactor for these interactions responsible for the pathogenicity in question, such as MSRV-2 or the gliotoxic factor described in the patent application published under the No. FR-2,716,198, can participate in the development of an overall and very effective strategy for therapeutic diagnosis, prognosis, monitoring and/or integrated therapy for MS in particular, but also for any other disease associated with the same agents.
In this context, a parallel discovery has been made in another autoimmune disease, rheumatoid arthritis (RA), which has been described in the French patent application published under the No. FR-2,731,356. This discovery shows that, by applying methodological approaches similar to those which were used in the studies by the applicant on MS, it has been possible to identify a retrovirus expressed in RA which shares the sequences described for MSRV-1 in MS and also the coexistence of an MSRV-2-associated sequence which is also described in MS. As regards MSRV-1, the sequences commonly detected in MS and RA relate to the pol and gag genes. On the basis of current knowledge, it is possible to combine the gag and pol sequences described with the MSRV-1 strains expressed in these two diseases.
The present patent application has as its object various results, supplementary in relation to those already protected by the French patent applications:
No. 92/04322 of 3 Apr. 1992, published under No. 2,689,519;
No. 92/13447 of 3 Nov. 1992, published under No. 2,689,521;
No. 92/13443 of 3 Nov. 1992, published under No. 2,689,520;
No. 94/01529 of 4 Feb. 1994, published under No. 2,715,936;
No. 94/01531 of 4 Feb. 1994, published under No. 2,715,939;
No. 94/01530 of 4 Feb. 1994, published under No. 2,715,938;
No. 94/01532 of 4 Feb. 1994, published under No. 2,715,937;
No. 94/14322 of 24 Nov. 1994, published under No. 2,727,428;
No. 94/15810 of 23 Dec. 1994, published under No. 2,728,585; and
Patent Application WO 97/06260.